冷泉渗漏区海底微生物作用及生物标志化合物

BIOMARKERS AND BACTERIAL PROCESSES IN THE SEDIMENTS OF GAS SEEP SITE

在有冷泉活动和水合物产出的海底环境中,甲烷氧化古细菌和硫酸盐还原细菌十分发育,它们主导着海底天然气(主要是甲烷)的缺氧氧化作用,并在海底碳循环和生物种群繁衍中发挥着重要作用。海底天然气渗漏活动区的甲烷氧化古细菌使渗漏CH4缺氧氧化为HCO3-,硫酸盐还原细菌使SO42-转化为HS-,从而使细菌微生物获得生命所需的能量,生物种群得以发育和繁衍。甲烷氧化古细菌有ANME-1、ANME-2、ANME-3三个种群,形成相应的醚类异戊二烯类和类异戊二烯烃类生物标志物。硫酸盐还原细菌有Desulfosarcina和Desulfococcus两个主要的细菌群落,形成二烃基甘油二醚和脂肪酸生物标志化合物。这种天然气渗漏区内微生物活动产生的生物标志化合物都具有特别负的碳同位素组成,δ13C值为-41.1‰^-95.6‰,说明微生物群落在生命代谢过程中摄取了来自甲烷的碳,同时也反映了天然气渗漏系统缺氧带存在的古细菌和硫酸盐还原细菌活动。

Methane oxidizing archea （MOA） and sulfate reducing bacteria （SRB） are abundant in cold seep and hydrate sites, where dominant anaerobic oxidation of methane played an important role in the sea carbon cycle and microbial propagation. MOA oxidizes methane into HCO3^- and SRB reduces SO4^2- into HS- at gas seep site, which is anaerobic, and microbes obtain energy here for living and growth. At least MOA consists of three colonies ： ANME-1, ANME-2 and ANME-3, showed in biomarkers as isoprenoids and free isoprenoid hydrocarbons. There are two colonies of SRB,that is, Desulfosarcina and Desulfococcus. The typical biomarkers produced by SRB are Dialkyl glycerol diethers （DGDs） and fatty acids. All the biomarkers of cold seep sites have very low carbon isotopic compositions which are between -41.1‰- 95.6‰, indicating that the microbes get carbon from CH, and that there are activities of MOA and SRB in anaerobic gas seep sites.